This invention relates to lens-fitted film units. Particularly, this invention relates to a lens-fitted film unit wherein an effective aperture diameter of a taking lens can be varied either by moving the taking lens in the direction of an optical axis or by changing an aperture diameter of the taking lens.
A lens-fitted film unit, which includes a photographing mechanism containing a taking lens and a shutter and provided with a roll of unexposed film loaded in advance in the main body during the process of manufacture, is disclosed, for example, in Japanese registered utility model publication No.2,564,847. The lens-fitted film unit of this type is so constituted an exposed portion of the film is taken up into the cartridge each time a picture is taken. Users may buy the unit and takes the unit itself to a photo developing shop to have it developed after the film roll has been finished. Therefore, the unit has gained wide market acceptance as a convenient and functional photographing product.
The lens-fitted film unit generally includes a single lens or two-piece lens structure in order to simplify the structure and bring down the cost of manufacture. The taking lens is fixed to the main body and focused on one particular focusing position. Therefore, an out-of-focus condition is avoided by making the depth of focus of the taking lens greater for objects which are not at the focused point. However, in recent years, variety of lens-fitted film units have been developed in respect of picture sizes and focal lengths of the taking lens. Thus, there are demands for products of various functions.
In such diversified lens-fitted film units, it is required to set the focused position of the taking lens accurately in the process of manufacture in case where a taking lens of a large focal distance is adopted it is necessary to adopt a variety of schemes for the lens positioning mechanism. For example, in Japanese laid-open patent publication Hei7-261069, there is disclosed a mechanism adapted to be used during manufacture of a lens-fitted film unit having a telephoto lens for positioning the lens at a precisely focused position and securing the lens at the position. However, even in such a lens-fitted film unit provided with the aforementioned focus setting mechanism, it is not possible to shift the taking lens to a plurality of focusing positions because the lens is fixed to the predetermined position once the focus position is thus determined. Taking such situations into consideration, it is desirable that lens-fitted film units and other cameras of simple structures have a structure which includes a single or two-piece lens structure but nevertheless can be adapted for a plurality of different photographing situations such as a close-up photographing, a normal photographing, and a photographing of distant objects, and can take properly focused pictures. In Japanese laid-open patent publication Hei10-200834, there is proposed a lens-fitted film unit having a taking lens of a short focal distance and capable of taking a photo of a very closely situated object, such as the one located within 60 cm, the unit including a reflex finder adapted to be moved into and out an operative position in front of the unit. In the operative position, the reflex finder makes it possible for a user of the unit to observe the filed of picture from the front side of the unit. Therefore, it is possible for the user to take a picture including himself or herself in the filed of the picture.
Thus, it is the actual circumstance that even in such lens-fitted film units characterized by their simple structure and low price, there are also trends of progressive diversification of their functions. In a lens-fitted film unit including a taking lens of a fixed focal distance, in order to make the focus adjustment position of the taking lens changeable between a normal photographing position and a close-up photographing position, it is necessary to make the taking lens movable in the direction of an optical axis. It is also necessary to make the taking lens movable in the direction of the optical axis where the taking lens is of a type wherein the focal distance can be changed between for example a normal distance and a telephoto distance. In this case, an angular field of a photographing peripheral light which extends between an outer edge of the taking lens aperture and an outer periphery of the exposure area or focal plane of the film is changed when the taking lens is moved between a retarded position and an advanced position. A similar situation is also created when the diameter of the taking lens aperture is adapted to be variable. More specifically, defining the term xe2x80x9ceffective aperture diameterxe2x80x9d as the diameter of the taking lens aperture at a predetermined axial position of the taking lens, the effective aperture diameter is varied in response to a movement of the taking lens in the direction of the optical axis. Similarly, the effective aperture diameter is also varied when the aperture diameter of the taking lens is changed.
On the other hand, since the lens-fitted film unit has to essentially have a photographing function, it is required to provide a making frame for blocking an unnecessary peripheral light in order to prevent so called ghost images and flare spots caused by internal reflection of a harmful light in an optical path which extends from the taking lens aperture to the exposure area on the film surface. In the lens-fitted film unit having an optical system in which the effective diameter is adapted to be variable as described above, it is preferable that the making frame is formed to be adjustable to match with respective peripheral light paths of photographing lights corresponding to each effective aperture diameter. However, such an adjustable structure of the making frame results in increased complexity and cost of the lens-fitted film unit.
It is an object of the present invention to provide a fixed making frame having a simple structure which can prevent ghost images and flare spots caused by internal reflection of a harmful light and substantially causes no decrease in quantity of a peripheral light, in a lens-fitted film unit having a photographic optical system in which the taking lens is adapted to be movable in the direction of the optical axis so as to change the focus adjustment position or the focal distance of the taking lens, or the diameter of the taking lens aperture is adapted to be variable, to thereby cause a change in the effective aperture diameter of the taking lens.
In order to solve the above mentioned problem, a lens-fitted film unit in accordance with the present invention comprises a taking lens, a photographic lens aperture provided in association with the taking lens and a unit body having a photographing mechanism including a shutter. The unit body is formed with a cartridge chamber for storing a cartridge shell having a rotatable spool provided therein for retaining an end of a photo film strip, and a film roll chamber for storing a roll of unexposed photo film strip withdrawn out of the cartridge shell, wherein the cartridge shell and the roll of an unexposed photo film strip withdrawn out of the cartridge shell are charged in advance during manufacturing in the cartridge chamber and the film roll chamber, respectively. A portion of the unexposed film is adapted to be positioned by an exposure frame which defines an exposure area between the film roll chamber and the cartridge chamber, and a portion of an exposed film is adapted to be taken up into the cartridge shell after each shot of photographing by rotating the spool. Further, a fixed making frame for blocking the peripheral light is disposed between the taking lens aperture and the exposure frame. As a feature of the present invention, the effective diameter of the taking lens aperture is variable to make an angular field of photographing light which extends from the taking lens aperture to an outer periphery of the exposure area is smaller when the effective diameter is large than in the case where the effective diameter is small. In addition, a predetermined width of the peripheral portion of the exposure area defines a non-print area, and the fixed making frame is disposed at a position closer to the taking lens aperture with respect to an intersection between a peripheral light which extends between an inner periphery of the non-print area and the taking lens aperture, under a large effective diameter of the taking lens aperture, and a peripheral exposure light which extends between the taking lens aperture and an outer periphery of the exposure area, under a small effective diameter of the taking lens. The making frame is of a size to partially or fully block the photographing light outside the peripheral light, which extends between the inner periphery of the non-print area and the taking lens aperture under a large effective diameter of the taking lens.
In the effective diameter of the taking lens aperture may be changed by a movement of the taking lens in the direction of the optical axis. In this case, the taking lens may be of a fixed focal distance type, wherein the movement of the taking lens in the direction of the optical axis cause a change in the focus adjustment position. Alternatively, the taking lens may be of a variable focal distance type, and the movement of the taking lens in the direction of the optical axis may be adapted to change a focal distance. Further, the effective diameter of the taking lens aperture may also be varied by changing the aperture diameter of the taking lens.
In another aspect of the present invention, a lens-fitted film unit comprises a taking lens of a fixed focal distance type, a lens aperture of a fixed aperture diameter, provided in association with the taking lens and a unit body having a photographing mechanism including a shutter. The unit body is formed with a cartridge chamber for storing a cartridge shell having a rotatable spool provided therein for retaining an end of a photo film strip, and a film roll chamber for storing a roll of unexposed photo film strip withdrawn out of the cartridge shell. Then, the cartridge shell and the roll of an unexposed photo film strip withdrawn out of the cartridge shell are charged in advance during manufacturing in the cartridge chamber and the film roll chamber, respectively. The unexposed film portion is adapted to be positioned between the film roll chamber and the cartridge chamber by an exposure frame which defines an exposure area therebetween and an exposed film portion is adapted to be taken up into the cartridge shell after each shot of photographing by rotating the spool. Further, a fixed making frame for blocking the peripheral light is disposed between the taking lens aperture and the exposure frame. In this aspect of the present invention, a taking lens is adapted to be movable in the direction of the optical axis for changing the a focus adjustment position, so that an angular field of a photographing light which extends from a taking lens aperture to an outer periphery of the exposure area is smaller when the taking lens is in an advanced position than, in a case wherein the taking lens is in a retracted position. A predetermined width of the peripheral portion of-the exposure area defines a non-print area, and the fixed making frame is disposed at a position closer to the taking lens aperture with respect to an intersection between a peripheral light which extends between an inner periphery of the non-print area and the taking lens aperture in the advanced position of the taking lens, and a peripheral exposure light which extends between the taking lens aperture and an outer periphery of the exposure area in the retraced position of the taking lens. The making frame is of a size to partially or fully block the photographing light outside the peripheral light which extends between the inner periphery of the non-print area and the taking lens aperture in the advanced position of the taking lens.
In a lens-fitted film unit according to the present invention, when the optical system is switched to the position where the effective diameter of the taking lens aperture becomes larger, the light which reaches the non-print area on the periphery of the exposure area among a photographing light under the large effective diameter of the taking lens aperture is partly blocked by the making frame causing a decrease in quantity of light in the periphery of the exposure area. However, it substantially causes no problem because this portion can usually be cut off from the photograph at a printing process.
When the optical system is switched to a position where the effective diameter of the taking lens aperture becomes smaller, a light outside a line which extends between the taking lens aperture and the peripheral portion of the exposure area under the small effective diameter of the taking lens aperture is passed through the making frame. However, the quantity of light can be reduced compared with the case where the size of the making frame is defined to pass the photographing light which reaches the peripheral portion of the exposure area under the large effective diameter of a taking lens aperture.
Therefore, in the condition that the optical system is switched to the position where the effective diameter of a taking lens aperture becomes smaller, only petty quantity of light can be passed through the making frame and reach the portion outside of the exposure area. Thus, there is substantially no problem of ghosts or flares.
Further, a second making frame may, if required, be provided at a position closer to the film surface with respect to the intersection of the lights described above. In the condition that the optical system is switched to a position where the effective diameter of a taking lens aperture becomes smaller, a harmful light can be completely blocked by setting the size of the second making frame capable of blocking a light outside the photographing light path which extends the taking lens aperture and the peripheral portion of the exposure area.